Protective relay



March 91 1926. 1576,119 C. l. HAFL' PROTECTIVE RELAY Filed August 8, 1924 Il fiventor: Chester L Hall,

I H is Attome .Patiited Mar. 9, 19 26.

iUNil-TED STA- Es PATENT r cnns'rnn r. :HALL, F 1 roar wnynn,mnmnn, ASSIGNOR T0 GEN RA nnnormc company, A CORPORATION or NEW YORK.

rnoracrrvn RELAYL] Application .filed August To all whom it mayconcem: 1 Be it known that I, CHnsyrnalI. HALL, a citizen ofthe United States, residing at Fort Wayne, in the c'ountyfo-f Allen, State of Indiana, haveinvented certain new. and .useful Improvements in- Protective- Relays, of which the following is -a specification.

. The present invention'relates to protective relays for electric translating devices, particularly temperature relays which are arranged to duplicate theheating ;characteristicsof the electric translating devices to be protected, and the object of the invention is to provide asimpl'e and effective device of the above "character embodying means for changing the current carrying capacity thereof without changing its thermal characteristics. p 1

One form of temperature relay to which my present invention is applicable is described fully and claimed broadly in my prior Patent No. 1,501,017 of July 8, 1924:.

Such a relay isdesigned to protect an electric translating device, as for example a inc-- tor, a transformer or: the like, from injurious heating under overload or other I abnormal temperature conditions by dupli eating the thermal characteristics of the device'in the relay itself. As more fully set forth in my above patent, a preferred form of the relay consists of athermal responsive element which carries the load currentof the electric device to be protected and also is in heat conducting relation with a heat storage mass which is provided-With an electrical heating coil connected in series circuit with I the thermal responsive. element. Ithe thermal responsive element is proportioned so pi portioned so as to duplicate the thermal "as to du licate the thermal characteristics.

of the winding of the translating device to be protected and the heat storage mass is characteristics of the frame of'the translating device. I v The resulting time load heating character- :istic of the relay is such as to duplicate that .erating eonditions. r I

I It is often desirable to vary the current carrying capacity of a temperaturerelayof the above type to enable the'relay affordprotection to an. electrical translatmgjde 'vice having a similar' thermal characteristic .but of greater current rating than that of of the device being protected under all opthe device which the relay was initially de- 8, 192 4. Serial No. 730,985.'

V signed to protect. Due to the predetermined OFFICE.

are arranged tobe heated to an operating temperature at different rates under varying condltions of overload. A shunt around'the -.entire relay is objectionable since the dis tribution of the current between the shunt and the relay will vary under different conditions of overload and hence the relaywill fail to duplicate accurately the heating characteristics of the machine to be protected.

Furthermore, to increase the rating of the.

relay by shunting the terminals thereof vwould involve an increased wattage loss which is-proportional to the increase in capacity and this is undesirable. Also the liability'of mechanical derangement or misadjustment of such a shuntin service is a very serious objection. v

- However, by means of my invention the current carrying capacity of the relay is increased withoutchangingthe amount of current carried by the thermal responsive element or the wattage loss in the relay and thus the thermal characteristics of the relay remain unchanged? Briefly, the inc ease in current carrying -capacity of the relay is effected according to my invention by providing a shunt which is arranged to by-pass the increased current only from the thermal-responsive element heat storage mass and at the same time vary- 'ing thev heating coil'for the storage mass so that the heat generated therein with the increased current combined with thatgener- -ated in-the shunt is substantially the same as wassupplied by the heating coil alone with normal current.

Fora better understanding of my invention reference is had to the following de: scription' in connection with the accompany- "ing'.dranivin-gin which the single figure is a perspective view of a temperature relay eriibodying the invention.

and conduct the heat generated thereby to the I is arranged to move into contacting engage-- 15 Referring to the drawing, the temperature relay illustrated comprises a thermal responsive element of the bi-metallic type, a heat storage mass 11 and an electrical heater 12. The heat storage mass 11 is divided into two parts which preferably are separated by an insulating partition of asbestos or the like'and the thermal responsive element 10 is mounted upon suitable shoulders or bosses formed upon each portion of the thermal storage mass 11 so as to be'in both electrical and heatconducting relation therewith. The free end of 'the element 10 ment with the stationary contact 13 when the element 10 is heated toa predetermined Y, temperature. ing coil 12 is connected at one end to the It will be seen that the heatrelay terminal 14 and at the other-end to the left hand portion of the heat; storage mass 11.

In order to increase the current carrying capacity of the relay according to my.1n- I venti'on,- a shunt 15 for diverting V the increased current from the thermal responsive element 10 is formed of a strip of suitable 'resistance material suchas advance ribbo'n which may be slotted as shownto permit one end thereof to be secured in intimate heat conducting relation with each portion of the storage mass 11 and at the same time furnish apath of suitable ohmic resistance in shunt with the thermal element 10. If the capacity of the relay is increased for example three times the resistance of, the

shunt would be one half that of the thermal element.

It will be observed that 'withthis arrangement the heating effect of thev current through shunt 15 is transmitted to the heat storage mass 11 rather than the thermal responsive element 10. This permits the heating coil l21tobe redesigned with a lower a resistance such that with the increased current, the watt loss therein plus the watt loss in the shunt 15 isthe same as the watt loss of the heater alone in the original relay.

Since the physical proportions of the thermal element 10 and the heat storage mass 11 remain unchanged and also the watt loss applied to heating these respective elemerits with the increased capacity is the by to said storage mass.

2. The combination with a temperature relay having a divided storage mass of metal and a current carrying thermal element in electrical and thermal connection witheach J portion of said storage mass, of a shunt for said element in heat conducting contact with each portion of said storage mass.

3. In a temperature relay, the combination of a heat storage mass, an electrical 5 heater therefor, a thermal responsive element connected ineircuit with said heater and in heat conducting relation with said storage mass, and a shunt for said element in heat conducting contact with said mass.

4. In a temperature relay, the combination of a'divided storage mass of metal, a bimetallic thermal element electrically and thermally connected toeach portion of said .mass, and means for heating said mass come prising a resistor in series connection with said element and a resistor in shunt connection with said element.

In 'witness whereof, I have hereunto set hand this 4th day of August,v1924.

' CHESTER I. HALL. 

